At present, computer output data are printed out with the aid of alphanumeric printers using the same character faces and size. In rapid printing of such matter as reference books, cataloques, promotional booklets and other documents, the information printed on alphanumeric printers must be reprinted by conventional processes, which takes much more time.
In another application area, i.e. textual information processing systems using photocomposition, proofs are produced either on alphanumeric printers using ordinary paper or with the aid of automatic photocomposing machines on silver halide materials. In this case, electrographic or diazotype duplicating machines are used.
Known in the art is an electrographic photocomposing machine (cf. U.S. Pat. No. 3,768,384; Cl. 95-4,5; 1973) comprising a regularly rotating type carrier with a flashtube provided with a control unit, a photographic unit, and a line forming mechanism. The photocomposing machine also comprises an electrophotographic section including a regularly rotating cylindrical intermediate image carrier coated with a selenium layer and optically associated with the line forming mechanism, a charging device with a lamp for exposure of the intermediate image carrier, and a latent image developing device. The electrophotographic section also includes a powder image transferring device and a unit for fixing the powder image on the paper with heaters. The machine also comprises a computer unit electrically associated with the drive of the line forming mechanism and coupled to the control unit of the flashtube.
In this prior art photocomposing machine, the recorded image can be duplicated only once. This is due to the fact that the dark resistance of the selenium layer (the resistance of said layer in the absence of light) is not sufficiently great. In this case, the potential relief induced on this layer relaxes much faster than required for reproduction.
Also known is an electrographic photocomposing machine (cf. patent specification of U.S. Ser. No. 72,555 for an "Electrographic Photocomposing Machine" filed on Sept. 4, 1979, now U.S. Pat. No. 4,226,514) comprising a rotary type carrier with negative images of characters, provided with a flashtube having a control unit, a photographic unit arranged downstream of the type carrier along the beam from the flashtube, a line forming mechanism arranged downstream of the photographic unit along the beam from the flashtube and provided with a drive. The machine also comprises an electrophotographic section including a cylindrical intermediate image carrier coated with a photoconductive layer, optically associated with the line forming mechanism and having a drive of its own, a charging device having a main charger in direct proximity to the intermediate image carrier, and a main lamp for exposure of the latter. The electrophotographic section also comprises a latent image developing device contiguous with the surface of the intermediate image carrier and arranged in the direction of its rotation downstream of the charging device, and a powder image transferring device with a paper feed system having a drive, which ensures mechanical contact between a paper web, the intermediate image carrier and is arranged downstream of the latent image developing device in the direction of rotation of the intermediate image carrier. In addition, the electrophotographic section includes a device for cleaning the intermediate image carrier, arranged downstream of the powder image transferring device in the direction of rotation of the intermediate image carrier, and a unit for fixing the powder image on the paper with heaters arranged near the paper web, on the side of the powder image, downstream of the powder image transferring device in the direction of motion of the paper web. The photocomposing machine also comprises a computer unit electrically associated with the line forming mechanism drive and coupled to the drive of the intermediate image carrier.
However, the known electrographic photocomposing machine fails to provide for multiple reproduction of an image recorded once on the intermediate image carrier because the dark resistance of the photoconductive layer is relatively small, and the potential relief relaxes within a period of time much shorter than required for reproduction.
Besides, the use of a corona discharge to transfer the powder image to the paper in the powder image transferring device of the known machine results in an additional charge being introduced onto the photoconductive layer surface, which destroys the potential relief after one or two reproductions.
Therefore, for duplicating copies produced on such a machine additional duplicating facilities are required, and this is time-consuming and involves additional equipment, hence increasing the cost of printing.